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| author | Tom Zanussi <tom.zanussi@linux.intel.com> | 2019-02-04 15:07:24 -0600 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-03-05 08:47:46 -0500 |
| commit | 9f0bbf3115ca9f91f43b7c74e9ac7d79f47fc6c2 (patch) | |
| tree | bc91b05a3507119c615c73a47b7bcbaedb4b39a0 /kernel | |
| parent | ed581aaf99be10883c8364df16bd80a7b8f72efc (diff) | |
| download | linux-9f0bbf3115ca9f91f43b7c74e9ac7d79f47fc6c2.tar.bz2 | |
tracing: Use strncpy instead of memcpy for string keys in hist triggers
Because there may be random garbage beyond a string's null terminator,
it's not correct to copy the the complete character array for use as a
hist trigger key. This results in multiple histogram entries for the
'same' string key.
So, in the case of a string key, use strncpy instead of memcpy to
avoid copying in the extra bytes.
Before, using the gdbus entries in the following hist trigger as an
example:
# echo 'hist:key=comm' > /sys/kernel/debug/tracing/events/sched/sched_waking/trigger
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist
...
{ comm: ImgDecoder #4 } hitcount: 203
{ comm: gmain } hitcount: 213
{ comm: gmain } hitcount: 216
{ comm: StreamTrans #73 } hitcount: 221
{ comm: mozStorage #3 } hitcount: 230
{ comm: gdbus } hitcount: 233
{ comm: StyleThread#5 } hitcount: 253
{ comm: gdbus } hitcount: 256
{ comm: gdbus } hitcount: 260
{ comm: StyleThread#4 } hitcount: 271
...
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l
51
After:
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l
1
Link: http://lkml.kernel.org/r/50c35ae1267d64eee975b8125e151e600071d4dc.1549309756.git.tom.zanussi@linux.intel.com
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 79e577cbce4c4 ("tracing: Support string type key properly")
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/trace_events_hist.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 5b03b9a869bb..c7774fa119a7 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -5157,9 +5157,10 @@ static inline void add_to_key(char *compound_key, void *key, /* ensure NULL-termination */ if (size > key_field->size - 1) size = key_field->size - 1; - } - memcpy(compound_key + key_field->offset, key, size); + strncpy(compound_key + key_field->offset, (char *)key, size); + } else + memcpy(compound_key + key_field->offset, key, size); } static void |